An off-duty Chicago Police officer fatally shot another man on the Northwest Side after an argument Monday morning, officials said.

The Cook County medical examiner’s office identified the slain man as 38-year-old Jose Nieves. Autopsy results released Tuesday found he died of multiple gunshot wounds, and his death was ruled a homicide.

He did not have a weapon, police spokesman Anthony Guglielmi said.

“I have a lot more questions than I do answers at this time,” Chicago Police Supt. Eddie Johnson said during a briefing with reporters Monday. “I came out because I wanted to make sure that the investigation was done properly.”

Johnson said the officer, a 57-year-old man assigned to the mass transit unit, does not live in the area and knew the person he shot from another “confrontation a few weeks ago.”

An “altercation” between the men escalated about 9:30 a.m. in front of a residence in the 2500 block of North Lowell, and the officer shot him multiple times, according to a police statement. Nieves was taken to Illinois Masonic Medical Center, where he died at 9:51 a.m., authorities said. His home address was unknown.

The police department and Independent Police Review Authority have opened simultaneous investigations into the shooting,

Guglielmi said police are still canvassing the area for witnesses and any surveillance footage. The shooting happened on the same block as Kelvyn Park High School.

Siclaly Mandujano, 16, and her family have lived a half block south of the shooting scene for five years and was at home when she heard three shots fired. She said she hears gunfire in the area at least once a month.

She sat on her front porch, holding her dog, a chihuahua-Jack Russell terrier-poodle mix, named Lucky, as police closed off traffic on the block.

“I have two older brothers and it’s kind of dangerous for them,” Mandujano said. “They’re not in anything bad or anything, but it’s dangerous for them.”

Contributing: Jordan Owen